[Terramor Bob]

The small rear side window does not go up sometimes. The door switch was replaced but did not solve the problem.
Garage with Mercedes diagnostic computer say it is the regulator motor. Has any one else had this problem and did motor replacement fix it? Should any lubrication be applied to the regulator slotted guides also?

 

[jaguartvr]

I had a similar problem. The drain tube had blocked and the window cables were sitting in water. They had started to rust causing the window to stick and eventually the cable snapped. A 2nd hand replacement fixed the problem. If you keep the drain hole clear and spray some lithium grease on the cables and pulleys you should avoid the problem.